Amend an object in an array

Question

I need to amend the amount to add £ before the number and change it to two decimals i.e. 9ドル.00

const data = [
 {
 title: 'Todo',
 amount: 9.99,
 },
 {
 title: 'In-Progress',
 amount: 4,
 },
 {
 title: 'Completed',
 amount: 10,
 },
 {
 title: 'Short',
 amount: 15.48,
 },
];

I can't work out how?

• Diego D: are you just asking how to read and set properties of objects inside an array? anyway in general Number.toFixed(2) toFixed
• tevemadar: Does this answer your question? Format number to always show 2 decimal places

Answer 1

You could do that, or you could use the Intl.NumberFormat to change it to currency on-the-fly. That way you get to keep your data neutral, and let the browser/JS handle the transformation only when it's needed.

const data=[{title:"Todo",amount:9.99},{title:"In-Progress",amount:4},{title:"Completed",amount:10},{title:"Short",amount:15.48}];
const style = { style: 'currency', currency: 'GBP' };
for (const obj of data) {
 const currency = new Intl.NumberFormat('en-GB', style).format(obj.amount);
 console.log(currency);
}

If you still want to change the data this method is still preferable. map over the data, destructure the amount from the object, and return a new object with the transformed amount.

const data=[{title:"Todo",amount:9.99},{title:"In-Progress",amount:4},{title:"Completed",amount:10},{title:"Short",amount:15.48}];
const style = { style: 'currency', currency: 'GBP' };
function toGBP(amount) {
 return new Intl.NumberFormat('en-GB', style).format(amount);
}
const out = data.map(obj => {
 const { amount, ...rest } = obj;
 return { ...rest, amount: toGBP(amount) };
});
console.log(out);

Additional documentation

• Rest parameters

• Spread syntax

Answer 2

Just map through it and use .toFixed(2) for the decimal.

const data = [
 {
 title: 'Todo',
 amount: 9.99,
 },
 {
 title: 'In-Progress',
 amount: 4,
 },
 {
 title: 'Completed',
 amount: 10,
 },
 {
 title: 'Short',
 amount: 15.48,
 },
];
const mapped = data.map((n) => { return {title: n.title, amount: `£${n.amount.toFixed(2)}`}});
console.log(mapped);

Answer 3

You can use Number#toFixed(2) and Array#map() methods as follows:

const 
 data = [ { title: 'Todo', amount: 9.99, }, { title: 'In-Progress', amount: 4, }, { title: 'Completed', amount: 10, }, { title: 'Short', amount: 15.48 } ],
 
 out = data.map(({title,amount}) => ({title,amount:`£${amount.toFixed(2)}`}));
 
console.log( out );